CAPTT.T.ARY MOVEMENT OF SOIL MOISTURE. 6 



The work as planned and carried out embodied a study of the rate 

 and extent of capillary movement of moisture in columns of various 

 types of soil, where capillarity was assisted by gravity, where it 

 acted against gravity, and where gravity as a factor was eliminated. 



The columns in which gravity was to assist capillarity were inclined 

 downward at various angles from the horizontal; the columns in 

 which gravity was to act against the force of capillarity were inclined 

 upward at various angles from the horizontal; and the columns in 

 which the effect of gravity was to be eliminated as far as possible were 

 set horizontal. 



Inasmuch as evaporation is one of the factors that controls the 

 extent and rate of movement of soil moisture by capillarity, it was 

 decided to run each set of experiments in duplicate, except that one 

 column was to be covered on all sides and evaporation reduced to a 

 minimum, while the other column was to be uncovered and exposed 

 on one side to the air. 



It was essential to the plan of the experiments that the probability 

 of free water- as such entering the columns be reduced to a minimum 

 and jet have sufficient water enter the flumes to give something with 

 which to work. It was desired to have a high initial percentage of 

 capillary water, and at thesanie time eliminate free water. To accom- 

 plish this end it was decided to have a vertical lift- from the surface 

 of the water- in the tank to the bottom of the container of the soil 

 column proper of from 3 to -i inches. After several preliminary tests 

 a vertical lift of 4 inches was adopted and all columns except- the ver- 

 tical ones (unless otherwise stated) have a vertical "lift" of 4 inches 

 from the surface of the water in the tanks to any change in direction 

 of the column. That part of the soil column from the surface of the 

 water to the point- of change in direction has been termed the" wick " 

 in the discussion which follows. 



Air-tight joints were maintained and no water escaped from the 

 tanks except by the wick and no moisture from the columns except 

 by evaporation. To guard against the formation of a true siphon 

 within the soil column an air space was maintained upon at least one 

 side of the soil column throughout its entire length, in the columns 

 inclined downward. 



All water added to the tanks after the initial filling was measured 

 and recorded. At specified intervals the position of the outward ex- 

 tent of the wet area of soil was measured and these measurements 

 recorded. 



The experiments in which a moist soil was the source of moisture 

 rather than a body of free water differ hut little from those described, 

 except that evaporation was eliminated in all cases. ' 



The soil boxes were partially filled with a soil containing a known 

 percentage of moisture, greater than the wilting percentage, and the 



